In our International Patent Application PCT/AU2007/001229 we disclose a pool surface skimmer which is retrofitted to an existing pool and which operates over a greater variation in pool surface level than conventional built in skimmer boxes. The use of our retrofitted skimmer means that pools do not have to be topped up as frequently in response to loss of water through evaporation and splashing and one can wait for rain to top up the pool. This is particularly useful where water restrictions are in force.
Our retrofitted skimmer has an inlet at its base to receive a suction cleaner hose which must be closed off when the cleaner is not in use so that the surface skimming action is maintained. At present the only other solution we know of covers the skimmer box well completely with a vacuum or suction plate and the pressure to the suction cleaner is then regulated by having a relief valve online. The relief valves only purpose is to ensure that the suction cleaner hose pipe is not directly attached to the pump as this would generally provide far too much suction to operate most cleaners.
This pressure relief valve leaves the pool owner with a much smaller window of operation as it is generally positioned in the skimmer mouth and needs to be completely submerged to allow the system to operate. Numerous variations on this type of pressure relief valve have proven to be unreliable as they have moving parts that are under pressure such as gates and springs which cause sucking of air and de-priming and which also generate noise.